Diagnosing Torsades De Pointes Based on Correlation to QT Interval: A Systematic Review

Abstract

Torsades de Pointes (TdP) is a rare form of tachyarrhythmia which can potentially be fatal due to its tendency to degenerate into ventricular fibrillation. It is described as a polymorphic ventricular tachycardia characterized by twisting of the QRS complexes around the electrocardiogram (ECG) baseline in patients with a prolonged QT interval. Prolonged QT interval is known as long QT syndrome. Torsades de Poccurs most commonly in patients with an extended QT interval duration, and even though monitoring an ECG can assist in its prevention, there is no defined duration of a QT interval that can lead to an increased risk of Torsades de Pointes. So, it is hard to determine what QT interval constitutes enough risk for Torsades de Pointes to require intervention. The QT interval duration also depends on other factors, namely heart rate (HR) and other factors such as drugs, congenital diseases, and a combination of both. In this study, we considered various causes of QT prolongation but mainly focused on congenital diseases, drugs, or perioperative risk of QT prolongation and the correlation with the risk of impending TdP. By following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and researching studies on various databases, namely PubMed, Science Direct, Medline, and CiNii we were able to find various systematic reviews and articles showing the association between prolonged QT interval and its degeneration into TdP. This review encourages further research into this topic to understand the implications of QT prolongation and how it can help save the lives of patients with known long QT syndrome, or those on QT prolonging drugs with simple ECG monitoring and treatment for the respective cause.

Keywords: drug-induced long qt syndrome; long qt syndrome; qt interval prolongation; qt prolongation and risk of torsades; torsades; torsades de pointes (tdp).

Figure 1. ECG showing Torsades de Pointes

Image adapted with permission from Dr. Mike Cadogan, co-founder of Life in the Fast Lane (LITFL).

Figure 2. Normal ECG pattern with defining QT interval

ECG: Electrocardiogram

Figure 3. Identification of studies via databases and registers

AMSTAR 2: Assessment of multiple systematic reviews 2, SANRA 2: Scale for the assessment of narrative review articles 2, CCRBT: Cochrane collaboration risk of bias tool, NOS: Newcastle-Ottawa scale